Objectives of this research project are (1) to characterize the dispersion and dilution of gaseous and small-particle aerosol contaminants within a confined, ventilated space that simulates a biomedical research laboratory, or other work space, and (2) to detect and describe any deviations from the theoretical phenomena of perfect mixing of contaminant and air. For each experimental parameter or combination of parameters, a tracer gas will be released into the test space and concurrent air samples will be taken at numerous sampling points. The collected data will be statistically analyzed to (1) determine the spacial distribution of the tracer gas concentration, (2) determine the degree of mixing at the respective sampling points, (3) test for homogeneity of tracer gas concentration at the respective sampling points. The experimental apparatus and methodology that has been developed will be employed and perfected; experimental protocols will be developed for future studies of contaminant dispersion in laboratories and work spaces with diverse conditions of ventilation, contaminant release, local exhaust and containment equipment, and occupancy and personnel activity.